Sheet plasma device



2 Sheets-Sheet 1 O. A. ANDERSON SHEET PLASMA DEVICE ATTORNEY.

m A m m T D W. N 1, G V A M 1w m n A K mm m 0. 9 I. 3 Z 3 O 1 mm N vm mm m July 17, 1962 Filed Aug. 5, 1960 July 17, 1962 o. A. ANDERSON SHEET PLASMA DEVICE 2 Sheets-Sheet 2 Filed Aug. 5, 1960 VACUUM PUMP PRESSURIZED HIGH VOLTAGE SUPPLY SWITCH INVENTOR.

OSCAR A. ANDERSON BY 44d ATTORNEY.

considerable development work at this time.

United States Patent 3,044,945 SHEET PLASMA DEVICE Oscar A. Anderson, Oakland, Calif., assignmto the United States of America as represented by the United States Atomic Energy Commission Filed Aug. 5, 1960, Ser. No. 47,883 4 Claims. (Cl. 204-1932) The present invention relates to a pinch device for confining and heating an electrical plasma and more particularly to such a device forming a plasma in a fiat sheet between two conducting walls.

Electrical plasma-producing systems are the subject of In the present invention, heating is accomplished by rapidly 'compressing a large ,volume .of plasma into a much smaller volume, the increased density and temperature of particles greatly increasing the probability of a fusion reaction occurring. High energy neutrons and protons are produced in such fusion reactions; the relative yields and the energies depending upon the mixture of gases used. Thus the device may be utilized as a source of neutrons while the protons from the fusion reactions remain trapped in the plasma and contribute further to the overall temperature rise to obtain additional neutrons. The overall temperature of the plasma need not be that required for a self sustaining or thermonuclear reaction,

since the energy of a portion of the plasma ions will exceed the energy required for a fusion reaction and such reactions will occur even though the mean plasma temperature is below fusion temperature. may further be utilized as a source of hot plasma.

In plasma heating and containing devices, a type of apparatus has been developed which is referred to as the pinch device. In general, such devices are character- 3,944,945 Patented July 17, 1962 ice function of the proximity and the plasma is pushed back toward a median position between the two walls. Although the stability with regard to kinks was very advantageous and additional utilization time gained, the

triaXia-l device is less stable with regard to the sausage instabilities than the present invention.

The present invention retains the kink stability of the triaxial device and is at least neutrally stable with regard to the sausage deformations. That is, such sausage deformation may occur but there is no tendency for the deformation to grow or increase in magnitude as in the previous devices since the sausage or interchange instability occurs whenever a plasma is contained by a magnetic field having a concave boundary and the plasma and field tend to interchange positions, leading to instability. The intensity of the instability decreases with increase in radius of the curvature of the magnetic field. In the present invention the radius of curvature for the magnetic field is infinite, thereby obtaining the neutral stability.

The present invention utilizes a pair of parallel conductive plates with electrodes suitably arranged so that a flat sheet or ribbon of plasma is formed between the The device ized by a very heavy discharge through a suitable gas between two electrodes, forming a plasma comprised of ions and electrons. The magnetic field surrounding the discharge exerts an inward force thereon .which compresses and heats the plasma. For instance, if the plasma chamber is cylindrical, the plasma is compressed into a narrow central rod-like configuration. However,

plates. The magnetic fields which pinch and contain the plasma are parallel to the plates and therefore meet the requirement for neutral stability, such fiat fields being established perpendicular to the direction of current flow through the plasma. 7

It is an object of the present invention to provide a new fusion device for producing a heated plasma.

It is another object to provide a pinch type plasma containment device having a novel flat configuration for producing a sheet plasma.

It is yet another object to provide a plasma containment device having increased plasma stability.

It is another object of the invention to provide a plasma containment and heating device having neutral after the plasma has been compressed for a very short time, certain instabilities form which distort and eventually disrupt the plasma rod before any substantial practical usage can be obtained. In general, there are two important types of instabilities, identified as the kink and the sausage or interchange. The kink instability results when the plasma rod bends, the bend or kink rapidly increasing in magnitude until the plasma either strikes the wall of the surrounding chamber or the rod is disrupted. Similarly, the sausage type of instability occurs when the diameterof one portion of the plasma rod is less than an adjoining portion,the instability increasing until the diameter of the smaller portion decreases to zero, again disrupting the plasma rod. Both of the above described instabilities are dynamic in that any slight perturbation of the plasma rod of the type described will rapidly increase in magnitude.

It was apparent with the rod shaped plasma that either the useful heating would have to occur before the instabilities disrupted the plasma or that some means of avoiding the instabilities should be sought. Following the latter course, the triaxial device (described in US. Patent No. 3,031,396, issued April 24, 1962 to 0. A. Anderson) was developed wherein a cylindrical plasma is formed between two coaxial conductive metal cylinders. The kink type of instability is suppressed by the formation of image currents in the adjacent metal walls which repel the pinched plasma through the resultant magnetic field. When the plasma approaches one of the walls the intensity of the repelling force increases as a stability with regard to interchange distortions of the plasma.

It is another object to provide a plasma device wherein a containing magnetic field has no curvature.

The invention, both as to its organization and method of operation, together with further objects and advantages thereof, will best be understood by reference to the following specification taken in conjunction with the accompanying drawing, in which:

FIGURE 1 is a longitudinal section view of the invention; 7

FIGURE 2 is a cross section view taken at line 22 in FIGURE 1;

FIGURE 3 is a longitudinal section view taken at line 33 in FIGURE 1; and

FIGURE 4 is a perspective view of the invention showing certain further components in schematic form.

Referring now to FIGURES l, 2 and 3 in conjunction there is shown acasing 11 of rectangular cross-section and formed, in this instance, by a shallow channel member 12 having a side plate 13 secured against the open side thereof. The channel member 12 and side plate 13 of the casing 11 are formed of an electrically conductive metal and define a chamber 14 of rectangular cross-section, the members being dimensioned so that to such fittings will subsequently be described with regard to FIGURE 4. A second end plate 24 is similarly attached to the opposite flange 18 which second end plate has a pressure line fitting 26 therein and apertures 27 for coaxial electrical power cables 29. An O-ring 31 is disposed between the flange 17 and first end plate 19 to maintain a vacuum seal therebetween. A circular recess 32 in the flange 17 adjacent plate 19 provides communication between the fittings 21, 22, and 23 and the chamber 14.

Adjacent the flange 18 are provided the supports and connectors for electrical power input. An insulative spacer 33 has an annular rim portion clamped between the second end plate 24 and the flange 18 in a circular recess 34 therebetween. The spacer 33 has a rectangular portion conforming to the inside dimensions of the casing 11 which portion extends inside the casing for a short distance, overlapping the quartz liner 16. A pair of O-rings 36 are disposed on both sides of the annular rim portion of spacer 33 for providing a vacuum seal between the spacer and the end plate 24 and flange 18. A metallic rectangular electrode 37, conforming in crosssection to the inside dimensions of the quartz liner 16, is secured to the spacer 33 by a pair of bolts 38. The center conductors of the coaxial cables 29 pass through suitably located apertures in the insulative spacer 33 and are electrically connected to electrode 37. The outer conductors of the cables 29 are electrically connected to the end plate 24 by clamp nuts 39 threaded into the apertures 27, the outer conductors thus being electrically coupled to the first end plate 19 through the casing 11.

An O-ring is disposed between the electrode 37 and spacer 33 for providing a vacuum seal therebetween. A recess 41 between the end plate 24 and spacer 33 provides communication between the pressure fitting 26 and the space around the cables 29. The pressurized air provides improved insulation in the space around the cables, suppressing arcing between the center conductor of the coaxial cable 29 and the end plate 24 which is connected to the outer shield conductor of the coaxial cables. The source of the potential applied to the coaxial cables 29, as well as other auxiliary components are shown in FIGURE 4.

Referring now to FIGURE 4, there is shown schematically the casing 11 with end plates 19 and 24 bolted to flanges 17 and 18 respectively. The gas inlet fitting 21 in the flange 17 is coupled to a gas supply 51 through a valve 52. A standard vacuum gauge 53 is coupled to the gauge fitting 23 while a vacuum pump 54 is connected to the pump fitting 22. Similarly, a pressurized air source n 56 is connected through a valve 57 to the pressure fitting 26 in the second end plate 24. The coaxial power cables 29 are coupled through a high current, high voltage switch 58 to a high voltage supply 59. The coaxial cables 29 are connected in parallel, the outer conductors thereof each being connected to ground and the inner conductors each being connected to the high voltage potential.

Considering now the operation of the device, and with reference to all figures, assume that the chamber 14 is evacuated by the vacuum pump 54. The valve 52 is then opened to let gas from the tank 51 into the chamber 14, such gas being a gas of low atomic number such as deuterium, a mixture of tritium and deuterium or the like. Pressurized air is applied to the region where the coaxial cables 29 connect to the device, the pressurized air suppressing arcing along the surface of the insulation around the center conductor of the cables. The high voltage supply may include means for charging a capacitor bank to provide a high current, high voltage source with low reactance so that by operation of switch 58 a powerful output pulse of energy having a short rise time is supplied to the electrodes. To obtain best operation of the pinch device, it is important that the pinch eifect be obtained rapidly from such a pulse of current. More than one power cable 29 is provided so that the impedance to a rapid current pulse is minimized.

When the switch 58 is closed, the power passes through the cables 29, passing from the center conductor of the cable 29 to the electrode 37, through the gas in the chamber 14 to the first end plate 19, and back through the casing 11 to the outside conductor of the coaxial cables 29. The quartz liner 16 prevents the discharge from occurring directly from the electrode 37 to the casing 11. The current immediately ionizes the gas in the chamber into a highly conductive plasma comprised of ions and electrons.

The magnetic field established by the discharge is at right angles to the direction of current flow through the plasma, such field causing a constriction or pinching of the plasma into a central ribbon or sheet at the center of the chamber 14. Immediately after formation of the pinched sheet, various instabilities are potentially present and are suppressed by the novel configuration of the apparatus. As previously described, image currents induced in the conductive walls aid in suppressing the kink deformations while the neutral stability of sausage deformations is obtained by the flatness of the pinch magnet-ic field. Such flat field follows the inside contour of the casing 11. instabilities may occur along the edge of the plasma sheet, but are sufliciently isolated from the central portion of the plasma to be disregarded in most instances. The desired nuclear interactions will generally have occurred in the central regions before such edge instabilities have time to increase in magnitude and disrupt the plasma in the central regions.

When the plasma is compressed, the density of the resulting plasma sheet is quite high, greatly increasing the plasma temperature and enhancing the number of reactions which occur. High energy neutrons and high energy charged particles are produced depending both upon the particular gas or mixture of gases in the chamber 14 and the particular reaction which occurs. The high energy particles or the heated plasma may be extracted for various purposes according to techniques well understood within the art. If a sufficient number of fusion reactions occur, the energy released thereby may exceed the input energy to the apparatus and a useful power ratio is obtained. The output energy may be either in the form of heat produced by neutron emission or in the form of electrical energy produced by the proton pressure against the magnetic field.

While the invention has been disclosed with respect to a particular embodiment, it will be apparent to those skilled in the art that numerous variations and modifications may be made within the spirit and scope of the invention and thus it is not intended to limit the invention except as defined in the following claims.

What is claimed is:

1. In a plasma device, the combination comprising spaced apart conducting planar walls forming a long chamber having a thickness substantially less than the width thereof, an insulative liner disposed along the inside surface of aid walls, a first and a second electrode each disposed at an opposite end of said chamber, a power supply coupled to said electrodes, and a gas supply communicating with the interior of said chamber.

2. In a plasma device the combination comprising a rectangular conductive casing forming a long rectangular chamber having a thickness considerably less than the width thereof, an insulative inner liner in said casing, a pair of spaced apart electrodes one at each end of said liner, a vacuum source communicating with the interior of said casing, a gas supply system communicating with the interior of said casing, and a power supply coupled to said electrodes for establishing a planar discharge between said electrodes proximal the interior walls of said casing whereby kink and interchange instabilities are avoided in said planar discharge.

an insulative liner disposed along the inside surface of said Walls, a first and a second electrode disposed at opposite ends of said chamber, said second electrode being electrically connected to said walls, a power supply, a transmission line coupled to said power supply and having a first conductor and a second conductor, said first conductor being connected to said first electrode, said second conductor being connected to said walls at a point adjacent said first electrode, and an ionizable gas supply communicating with the interior of said chamber.

4. In a plasma device, the combination comprising flat conductive spaced apart Walls forming a long chamber of rectangular cross-section, said chamber having a thickness substantially less than the width thereof, an insulative liner disposed along the inside surface of said walls, a first and a second electrode each disposed at an opposite end of said chamber, said second electrode being electrically connected to said walls, a power supply, a switch v said Walls being small with respect to the Width thereof,

connected to the output of said power supply, at least one coaxial cable connected to said switch and having an inner conductor and an outer shield conductor, said inner conductor being connected to said first electrode, said shield conductor being connected to said walls at a point adjacent said first electrode, a vacuum source communicating with the interior of said chamber, and an ionizable gas supply communicating with the interior of said chamber.

References Cited in the file of this patent UNITED STATES PATENTS Colgate et a1 July 26, 1960 OTHER REFERENCES Proceedings of the Second United Nations International Conference on the Peaceful Uses of Atomic Energy.

, Held in Geneva, September 1-13 (1958), vol. 32, pp. 125, 

1. IN A PLASMA DEVICE, THE COMBINATION COMPRISING SPACED APART CONDUCTING PLANAR WALLS FORMING A LONG CHAMBER HAVING A THICKNESS SUBSTANTIALLY LESS THAN THE WIDTHE THEREOF, AN INSULATIVE LINER DISPOSED ALONG THE INSIDE SURFACE OF SAID WALLS, A FIRST AND A SECOND ELECTRODE EACH DISPOSED AT AN OPPOSITE END OF SAID CHAMBER, A POWER SUPPLY COUPLED TO SAID ELECTRODES, AND A GAS SUPPLY COMMUNICATING WITH THE INTERIOR OF SAID CHAMBER. 